1. Field of the Invention
The present invention relates to a non-contact measuring device and, in particular, to a non-contact measuring device which, in accordance with scanning by use of a laser light or the like, measures the outer dimensions of objects to be measured (that is, works) which are delivered continuously from a conveyor or the like.
2. Description of the Related Art
In non-contact measuring devices according to the prior art, there is known a non-contact measuring device in which an object to be measured is interposed between a laser light projecting part and a laser light receiving part and the outer diameter and other dimensions of the object to be measured are measured in accordance with scanning by use of a laser light.
In the above-mentioned prior art non-contact measuring device, as shown in FIG. 4, a laser light generated from a semiconductor laser 302 is turned into a parallel light of radiation 306 bymeans of a lens disposed within the semiconductor laser 302, and the parallel light 306 is then reflected by a polygonal mirror 308 which rotates at a constant speed. The parallel light 310 is then refracted by a collimator lens 312 and is focused on the center line of an object to be measured 314 and at the focal distance of the collimator lens 312. Also, the beam refracted by the collimator lens 312 becomes a parallel light parallel to the optical axis of the collimator lens 312 and is then guided through a light receiving lens 316 to a light receiving element 318. For this reason, if a scanning area is scanned one time by use of the parallel light, then the diameter and other dimensions of the object to be measured 314 within the scanning area.
In this manner, in the conventional non-contact measuring device, a distance between the collimator 312 and the object to be measured 314 is set at the same distance as the focal distance f of the collimator lens 312.
However, when the conventional non-contact measuring device is used in various types of conveyors and the like, the distance f between the collimator lens and the object to be measured must be changed before it is used.
In this case, because the currently used collimator lens must be replaced by another collimator lens having a different focal distance f, various kinds of expensive collimator lenses must be prepared previously.